This invention relates to multilayered structures having one or more diamond layers and methods of making the multilayered structures.
An important problem in the electronics industry is how to dissipate the heat generated from a semiconductor device. The thermal energy must be sufficiently removed to avoid performance degradation or even failure. One mechanism involving heat transfer by conduction places a material referred to as a heat spreader adjacent to the semiconductor device. The rate of removal depends on the heat spreader's thermal conductivity and the thermal resistance of the bonding material between the semiconductor device and the heat spreader.
Diamond has desirable properties that should be useful in a heat spreader including high thermal conductivity, low electrical conductivity, high Young's modulus, wide bandwidth optical and EMR transmission, and extreme corrosion resistance.
Diamond's properties are difficult to exploit, however, because they do not match semiconductor devices' or metals' properties. For example, diamond's thermal conductivity is several times larger than copper or silver. Diamond's coefficient of thermal expansion is also substantially lower than that of many semiconductor devices. These differences also limit the bonding materials that can be used to avoid cracking or bending the semiconductor devices. Unfortunately, bonding materials that could be used have poor thermal conductivity and other problems such as electromigration and material creep effects. These problems limit the performance and reliability of the semiconductor device.
There exists a need for a structure that has a thermal conductivity which is similar to diamond and a coefficient of thermal expansion which can be matched to various semiconductor materials such as silicon, silicon carbide, gallium arsenide, and gallium nitride. Some products attempt to match the thermal expansion using copper layers bonded to both sides aluminum nitride or beryllium oxide. However, they have thermal conductivities which are typically no higher than their ceramic layer. Further, they must have thick layers of copper to attempt to match the expansion which limits the ability for patterned and electrically isolated regions on mounting surfaces.